Electric switch.



c. T. HENDERSON,

ELECTRIC SWITCH.

APPLHIATION FILED SEPT. 14. 1914.

11,269,278. Patented June 11, 1918.

2 SHEETS--SHEET I C. T. HENDERSON.

mama SWETCH.

APPLICATION FILED SEPT-14. 3914.

1,269,278. 7 intmtui June 1%, 1918.

2 SHEETSSHEEY H W y STATES PATENT OFFICE.

CLARK T. HENDERSON, 0F MELWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMER MFG. 00.. OF MILWAUKEE, WISCONSIN, A CORPORATION OF WIS- CON SINELECTRIC SWITCH.

Specification of Letters Patent.

Application filed September 14, 1914. Serial No. 861,599.

To all whom it may concern: 7

Be it known that I, CLARK T. HnNnEnsoN, a citizen of the United States,residing at Milwaukee. in the county of Milwaukee and State offivisconsin, have invented new and i i111)1()\'11l0flt$ in ElectricSwitches,

-clithe following is a full, clear, cond'exact description, referencebeing had to the accompanying drawing, forming a ial't of thisspecification.

his invention relates to improvements inseries switches. Switches havebeen de ised called series switches in which a single coil operates thecontacts and the magnetic circuit is so formed that the-coil will notclose the contacts so long as the current to which it is subjected isabove a predetermined value. This magnetic circuit has a portion ofrestricted magnetic cross-section which becomes saturated when thecurrent in the coil is above a certain limit. A shunt magnetic circuitis provided around the restricted circuit. When the coil is energizedwith a high current, the excess flux passes through the shunt circuitand acts on a means'which prevents the switch from operating. \Vhencurrent in the coil de creases, the flux dies out of the shunt circuit,the holding means becomes inactive, and the switch is allowed tooperate. The restricted magnetic circuit which'is a necessary element inthese switches gives rise to several lin'iitations hereinafter pointedout.

Switches of the above mentioned type are often equipped with contactswhich are closed against the pressure of a spring. It is desirable thatthe moven'ient against the spring pressure be for a considerable-'distance in order lO'COIllPCIlSElli? for wear on 1 the contacts. Theforce necessary to close thecontacts against the sprlng pressure islarger than that necessary to startthe movement thereof. For this andother reasons it "follows that the force acting on the contacts shouldbe at a maximum value as tl-lecontacts are moved to and held in closedposition.

The. restrictions on the magnetic circuit I Iches oi the type describedlimits the n ma mum closing pull for any given size i switch starts tooperate.

- n'iagnetic itcha glVlicn the operating coil and.

the movable parts are made of proper sizefor a given current, therestricted portion of the magnetic circuit must be limited to a propercapacity to insure that the switch will operate when the currentdecreases to a predetermined value. The capacity of the circuit when solimited i such that it is substantially saturated by the actuating fluxpassing through it at the time the It therefore cannot accommodate anincrease in lines of force and does not act as a return path for theincrease in flux. The result is, that as the armature moves to decreaseits air gap, the additional flux which would normally tend to threadthrough the armature and exert an additional pull thereon does not. doso for tne reason that the saturated restricted magnetic circuit doesnot provide a return path from the armature. Since there is nosubstantial increase in the amount of flux passing through the armatureas it decreases its air gap, the pull does not increase to the highnuiXimum dcsirable during final closing movement. Curve A in Fig. 4illustrates the change in pull on the armature as the air gap decreasesin a given size of switch having a restricted circuit. This curve showsa slight rising pull as the air gap first decreases but the curve dropsaway and becomes almost horizontal as the air gap becomes smallindicating that no substantial movement of the armature.

The restricted magnetic circuit thus limits the maximum closing pullobtainable in a given size of switch. An increase in pull on a givensize of contacts obtained by increasing the size of the coil,thearmature and the magnetic circuit, or either of them, above whatwould otherwise be neces sary to secure operation. on predeterminedcurrent, is objectionable for several reasons among which are that theswitch is more expensive and an increased space for installation isnecessary.

One of the objects of the present invention is to provide a magnet withmeans for increasing the pull on its armature after the armature hasresponded.

provide a magnetic structure in which the armature is actuated to andheld in. closed position in a positive and forceful manner.

Another object of the invention is to provide a switch in which thecontacts will be firmly forced to and held in closed position regardlessof limitations in the amount of flux available to start the switch.

Another object of the invention is to provide an electromagneticstructure in which an additional path is provided for the flux after themovement of thearmature has been initiated.

Still another object of the invention is to provide means for completingan additional magnetic circuit for the flux having a restricted magneticcircuit to thereby increase the pull on the armature as the switchcloses.

Various other objects" and advantages of my invention will hereinafterappear.

The accompanying drawings illustrate an embodiment of my invention andin said drawings Figure 1 is a side elevation of the switchembodying oneof the preferred forms of my invention.

Fig. 2 is a partial side elevation of a modified form.

Fig. 3 is a cross section of themodification shown in Fig. 2.

Fig. a represents the pull curve diagram explained in detailhereinafter.

Fig. 5 is a side elevation of another modification of, the invention. I

Figs. 6 and 7 are apartial side elevation and an. end view of amodification of thestructure shown in Fig. 5. 7

Figs. 8. and 9 are a partial side elevation and an end View of stillanother modification of the structure shown in Fig. 5. The switchcomprises in general a stationary contact 3, a cooperating movablecontact 4, amain switch frame carrying an operating coil 5 and amovablearmature 6 upon which thecontact 4 is mounted.

The switch frame, which also acts as a magnetic circuit, has a top 7 ofbrass or other non-magnetic material, a bottom Sof magnetic material anda side member 9 also of magnetic material. The :side 9 is of limitedmagnetic cross section. It. acts as a magnetic throttle in a mannerhereinafter described. 7

The non-magnetic top -7 of the frame causes, substantially all the fluxfrom the magnetic core 10 of coil 5 to normally pass across an air gap15 to armature 6. a The normal return path for this flux is througharmature 6, magnetic support 1 1, magnetic This circuit is side member 9to bottom .8.

of limited capacity since the-part -9 is of naeaere 17. The movablearmature structure is bal-'.

anced to normally rest in the position shown in Fig. 1 with the bar 16in engagement with the brass adjusting screw 18. The screw 18 regulatesthe length of air gap 19v be: tween bar 16 and pole piece 17 The shuntmagnetic circuit may be traced from core 10 through arn'iature 6, bar16, pole piece17, member 8 to core 10.

The movable contact 1 which is supported by the armature 6 may be of anysuitable type. It is shown in this instance as pivoted to the armatureby means of a bracket 12 and pivot 13. The bracket 12 is biased forwardby a spring lil: so that the contacts 4; and 3' engage before thearmature 6 seals with the. core 10.- The contact 4. is thereby given asufficient movement against spring .pressure after engagement to producea wiping action.

When the coil 5 is energized with a high current, the member 9 becomessaturated and the pull at gap 19 is'weahened because a greaterproportion of the flux is carried by the mei'nber 9. When the currentreaches a predeterminedvalue. the pull at gap 15 overcomes that at 19and the switch is closed.

Fig. 1 illustrates one form of means for securing a high maximum. pullon the armature. This means increases the pull in a given size of switchwithout materially effecting its predetermined current operatingcl1aracteristics The means may be embodied in a variety of forms. Itcomprises in general a means for completing an additional path for theliuxafter the armature 6 has started in its movcmenttoward core 10.

An extension 20 of magnetic material projects outwardly from the switchframe below the bar 16. This extension is curved approximatelyconcentric with the are described by the end of bar 16 and terminates ina head :21 which is engaged by the bar 16 when it reaches the dottedline position shown in Fig. 1. An additional path is thereby providedfor the flux, which path constitutes the armature 6, bar 16, head :21extension 20 and member 8. This Path becomes active as soon as the bar16 approaches close enough to the head 21 to enable the flux to bridgethe gap between said members. The additional path constitutes agoocl.return'c1rcu1t from the, armature for the increase in flux throughthe same as it approaches its core, and the pull on the armature isthereby greatly increased. A suppleinental pull is also exerted by head21 on bar 16.

The operation of the switch shown in Fig. 1 is as tollows,when the coil5 is energized, by high current, the flux saturates the part 9, and theexcess flux follows a path through bar 16 and gap 19. The pull at gap 19on bar 16 is more effective than the pull at gap 13 on armature 6. Theswitch is consequently held open. As the current in coil 5 decreasesthe. flux decreases until the greater proportion of it is carried by themember 9. The pull across gap 19 is thereby weakened and when thecurrent reaches a certain value the pull at gap 15 overcomes. that atgap 19 to close the switch. The movement of the armature 6 toward itscore throws bar 16 away from its pole piece 17, thereby opening themagnetic circuit through bar 16 and pole piece 17.

Further movement of the armature 6 causes the bar 16 to approach andengagethe head 21. An additional magnetic circuit is thereby completedfor the flux through the armature 6. The flux may accordingly increasethrough the armature 6 and exert an addi tional pull thereon to sealitwith the core in a firm, positive manner. The pull on bar 16 throughhead 21 supplements the pull of main armature 6.

Curve B in Fig. 4 of the drawings shows the manner in which the pullincreases the air gap decreases in a switch provided with an additionalpath such as above set forth. This curve may be compared with curve Arepresenting the pull in a switch of the same size and type without theadditional magnetic circuit. It will be noted that the pull on thearmature when the air gap is small and as the armature seals with itscore is much larger in curve B where the switch is equipped with anadditional. flux path.

Figs. 2 and 3 illustrate a modification of the extension 20 as appliedto a switch of the type shown. The head 21' of the extension 20 in themodification has two side members extending therefrom toward the polepiece 17 to form a channeblike member for receiving the bar 16. Thespace between the members made to accommo-' date the bar 16 with thesmallest clearance possible consistent with good mechanical operation.lVhen the bar 16 enters the space between members 23, a'magnetic circuitis completed through the bar across the small air gap to members 23 andback through the extension 20 to member 8 and the i'nagnet core. Anadditional path for the flux is thus provided before the armature 6 hascompleted its movement. This additional path causes the pull on thearmature an additional side member 26 terminating in a sloped-oft end27. ,The armature 6 is extended and provided with a head 28 which isbeveled to lit the end 27 of the side member 26 when the armature 6seals with its core. The shape of the part 27 and the cooperating head28 may be varied to suit different conditions, but the structure shownis found very desirable because the reluctance of the circuit decreasesvery rapidly as the head 28 moves toward the part 27. lVhen the armature6 moves toward its core, an additional magnetic circuit is completedthrough the armature extension 28 and the side member 26. This circuitbecomes active before. the part 28 actually seals with the part 2? sincethe reluctance of the circuit is rapidly decreased as the air gap 29 isdecreased. The length oi the air gap 29, when the switch is open. shouldbe so adjusted that the predetermined current operating characteristicsof the switch will not be materially affected. -The other parts of theswitch are. of the same structure as illustrated and described in Fig.'1 and the operation of the switch is in general the same.

Figs. 6 and '4" illustrate a modification of the structure shown in Fig.The upper end of the side 26 of the frame in this modification. has twomembers 32 extending upwardly therefrom. The armature 6 isprovided'with' an extension 31 which moves be tween the parts 32 andcompletes a magnetic circuit from the armature 6, through the extension31 to the side members and. This cir-- through the part 26 to the core.cuit is completed before the armature 6 has reached the limit of itsmovement and. an additional nia netic circuit thus provided at anearlier period in the movement of the armature than in the structureshown in Fig. The arms 32 may be made in various lengths to vary thepoint at which the additional magnetic circuit isgcomplcted in themovement of the armature.

Figs. 8 ant 9 illustrate another modification of the structure shown inFig. 5. The side is provided with a tapered end 3'5 which cotiperatcswith an opening 37 in an extension 36 of the armature 6. 36 moves overthe end 35 and completes an additional magnetic. circuit tln'ough thepart 36 member 35 and the side 26 to the core.

lvhile I have shown and The extension" described a preobvious that manychanges may be made in the details of construction and arrangement ofparts without departing from'the spirit v and scopeof the appendedclaims.

Having desc'ribedmy invention, what I claim and desire to secure byLetters Patent 1. An electromagnetic mechanism cornprising anelectromagnet, a movable armature, and means including a magneticcirbuit of limited capacity and an extension .of said armature formagnetically preventing movement of the armature when current in themagnet winding is high, said mechanism having a member for reversing themagnetic pull on said armature extension after it has responded.

2. An electrdmagnetic mechanism having amovable armature, an operatingwindin therefor, and means including a magnetic circuit of limitedcapacity for preventing movement of the movable armature when .theWinding is initially energized above a --a,- member with which themovable armature cooperates upon the movement thereof to (complete amagnetic circuit in shunt to the .-circ uit of limited capacity forincreasing the pull on the movable armature after movement thereof hasbeen initiates.

.3. An electromagnetic mechanism having "a movable armature, anoperating winding,

means by'which said winding eXterts a pull to move said armature and anopposite pull 3510 .hold the armature against movement when the initialcurrent in. the winding above a predetermined value, and a memberassociated with said mechanism and rendered active upon movement of them'ovable armature for causing some. of the hold- Zing Qux to assist inmoving the armature after the moving pull has overcome the hold ingpull. I

4. A magnetic mechanism having a movable armature, a main magneticcircuit havmg a portion of limited capacity, a magnetic circuit in shuntto said portion of the main circuit of limited capacity, the shuntcircuit including a portion of the movable armature. and a memberassociated with said mechanism by which said portion of the movablearmature completes a second magnetic circuit in shunt to the limitedcapacity circuit during movement thereof to increase the capacity of themain circuit to thereby increase the pullon the movable armature duringmovement thereof.

. 5. An electromagnetic mechanism having a movable armature, anoperating winding therefor, a magnetic circuit of limited capacity,means controlled by excess-flux for predetermined value, said mechanismhavingv estates the armature after movement thereof has been initiated.

6. An electromagnetlc mechanism having an operating winding, a movablearmature,

a main magnetic circuit including said armature, said circuit having aportion of limited magnetic capacity, said armature having a portionnormally forming a magnetic shunt to the portion of the main magneticcircuit oflimited capacity and said mechanism having a member by whichsaid portion of the armature completes another shunt magnetic circuit tothe portion of the main magnetic circuit of limited capacity as thearmature is moved to closed position.

7-. switch having a movable armature adapted to control the switchcontacts. an operating winding therefor, means by which said Winding: iscaused to extort an actuatinc; force in one direction on one part ofsaid armature and a holding force on another cart of said armature. anda member associated with said switch for causing some of the holdingflux to be reverse in direction of operation during movement of thearmature so that it assists the actuating force after the armature hasstarted to move.

8. A switch having; a single winding for operating its contacts, amagnetic circuit of limited capacity for the flux from the windinej.means controlled by excess flux from said circuit to prevent closure ofthe switch when the initial current in. the winding eX- coeds apredetermined value, and a member 190 associated with said switch forcompleting an additional path for the excess flux through.- said meansas the switch closes so that a high pull will be exerted on the switchduring closing movement thereof.

